As industrial cleaning methods of various materials, conventionally, use has been made in a wide variety of fields of solvent compositions containing CFC113 and 1,1,1,-trichloroethane with excellent incombustibility, low toxicity and good stability as the principal components. However, it has been remarked that various types of CFC, 1,1,1,-trichloroethane, and carbon tetrachloride and the like damage the ozone layer, leading to the absolute worldwide banning of the production of CFC113, 1,1,1-trichloroethane and the like since the end of 1995 and to the use thereof under regulation, from the standpoint of the protection of the ozone layer.
As alternatives of these CFC113 and the like, hydrochlorofluorocarbons such as HCFC225 and HCFC141b have been proposed and used practically. But a time limit is imposed to the use thereof because these have also damaging potencies of the ozone layer although the potencies are extremely low. Furthermore, conventional chlorine containing solvents including for example methylene chloride, trichloroethylene, and perchloroethylene are so problematic in terms of safety profile (oncogenesis and intoxication) that these have been also under various regulations or have been under way of regulatory controls.
Still furthermore, various compounds have been proposed, which can retain the advantages of these fluorine containing solvents, such as incombustibility and stability, but never contain chlorine atom as the essential factor for the ozone layer depletion. The compounds include for example those principally comprising perfluorocarbons such as perfluoro-n-heptane (WO 92-03205, etc.), those principally comprising acyclic hydrofluorocarbons (WO 95-06693, JP-W-6-501949) and those principally comprising specific cyclic hydrofluorocarbons (WO 95-05448).
For the purpose of endowing solid surface with lubricating properties, non-coherent properties, water-repelling properties, conventionally, a method has been used for forming a polymer film with lubricating properties, non-coherent properties, and water-repelling properties on solid surface by using a solution dissolving or dispersing a polymer therein.
As electronic devices, machines and appliances and parts have been down-sized and highly sophisticated, these are required to have high lubricating properties at the sliding parts and surfaces thereof. Lubricating properties and non-coherent properties at high precision, high durability and high reliability have been demanded specifically for sliding between hard disk, mini-disc, magnetic tapes such as digital audio tape or video tape, other magnetic record media or optical disks and record/read-out heads. For sliding between hard disk and record/read-out head, for example, a protective layer of carbon and the like is formed on a magnetic layer; and then, a polymer film comprising a lubricating fluoro polymer is additionally formed thereon. Because the sliding parts of machines and appliances such as cameras, video cameras, office machines, medical apparatuses, vacuum machines such as vacuum pumps, electronic parts, precision automobile parts, small motor, ultrasonic motor and micro-machine should be endowed with lubricating properties with high durability, high reliability and low staining properties, due to the demands for high performance and down-sizing thereof, polymer films comprising lubricating fluorine-series polymers are likely to be formed on the sliding parts of these machines and appliances. So as to securely impart discharge stability and orientation to polar liquids, polymer films comprising water-repellent fluorinated polymers are formed on the nozzle surface on the nozzle opening of inkjet recording head.
Conventionally, various propositions have been made regarding the method for forming polymer films on such solid surfaces. For example, a method comprises dissolving a polymer with a small surface tension, such as fluoro polymer with lubricating properties or water repellency, in an appropriate volatile solvent, coating the resulting solution on various materials or parts, and thereafter vaporizing the solvent to form a polymer film.
A solution prepared by dissolving a fluoro polymer in a fluorinated solvent has been known. CFC 113 (JP-A-5-342570) and perfluoro-n-heptane (JP-A-4-211959) are reported as such fluorinated solvents. However, the production and marketing of conventional CFC 113 is prohibited under the regulation against ozone layer layer-depletion substances, while perfluorocarbons such as perfluoro-n-heptane are disadvantageous because of the poor solubility so that a uniform fluorinated polymer film cannot be recovered.
JP-A-3-158884 describes a process of coating a dispersion prepared by dispersing polyvinylidene fluoride, a phenolic resin or tospearl in particles in a liquid medium selected from isopropyl alcohol, ethyl alcohol, CFC 113 and water on the contact part between the image carrier in an imaging apparatus and a member material in contact to the image carrier, and subsequently drying the dispersion. It is described that according to the process, the friction between the image carrier and a cleaning blade in contact to the carrier can be reduced, leading to the resolution of problems including blade peel off or non-uniformly charged state of the surface of the image carrier.
JP-A-3-197952 describes a process of spraying a dispersion of particles such as fluorine resin particles or silicone resin particles in an organic solvent on the surface of an electrophotographic photosensitive material and then drying the dispersion. The organic solvent including CFCs is exemplified. It is described that according to the process, the friction between the photosensitive material and the cleaning blade for removing residual toner is reduced, whereby the problem of blade peel off can be overcome.
Because these polymers with lubricating properties are not homogeneously dispersed or dissolved in the polymer-containing solutions, polymer films prepared by coating the polymer-containing solutions on solid surface and removing the liquid medium are not uniform on the solid surface. Hence, the effect of the polymer films to reduce friction on the solid surface cannot be exerted sufficiently.
As has been described above in detail, the perfluorocarbons and hydrofluorocarbons are preferable in terms of no concern of the ozone layer depletion, and good cleaning performance with great finish, when used as they are or in combination with organic solvents. Nevertheless, they individually have problems to be overcome. For example, perfluorocarbons have high global warming potentials, leading to the possible occurrence of new problems from the standpoint of the protection of global environment. Additionally, cyclic or acyclic hydrofluorocarbons of various structures have been proposed, but they are problematic, structurally. For example, hydrofluorocarbons of a structure with a --CF.sub.2 CHFCHFCF.sub.2 -- bond are disadvantageous in terms of poor stability in the presence of basic compounds or water.
It is the object of the first aspect of the invention of the application to provide a fluorinated hydrocarbon with excellent cleaning performance, great incombustibility and high stability in the presence of water, which can overcome the drawbacks of such conventionally known hydrofluorocarbons and can be produced readily, a method for producing the same and a solvent composition thereof, and a cleaning agent and a cleaning method, using the same.
It is the object of the second aspect of the invention of the application, to provide a polymer-containing solution and the like capable of forming a uniform polymer film on solid surface by sufficiently enhancing the homogenous dissolution of a polymer in the polymer-containing solution, and a process of forming a polymer film using the same, because a polymer-containing solution capable of forming a uniform polymer film on solid surface has been desired although conventional techniques for forming polymer film as described above can exert only a limited effect on the improvement of solid surface.